Electrical lead assembly with transformer



June 22, 1965 H. SEGALL ELECTRICAL LEAD ASSEMBLY WITH TRANSFORMER 2 Sheets-Sheet 1 Filed Nov. 6, 1961 4 1v 4' a 1 4 Ir;

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LOUIS H. SEGALL BY ATTOR YS June 22, 1965 L. H. SEGALL ELECTRICAL LEAD ASSEMBLY WITH TRANSFORMER 2 Sheets-Sheet 2 Filed Nov. 6, 1961 INVENTOR.

LOUIS H. SEGALL ATT NEYS United States Patent 3,191,103 ELECTRICAL LEAD ASSEMBLY WITH TRANSFORMER Louis H. Segall, Sidney, N.Y., assignor to The Bendix Corporation, Sidney, N.Y., a corporation of Delaware Filed Nov. 6, 1961, Ser. No. 150,454 7 Claims. (Cl. 317157.6)

This invention relates to electrical apparatus and more particularly to apparatus for producing electrical discharges of spark intensity. The apparatus of the invention is useful, for example, in ignition systems for engines of the jet and ram jet type.

The invention has among its objects the provision of an electrical apparatus, of the type indicated, including a novel voltage step-up transformer coil.

A further object of the invention lies in the provision, in spark-producing apparatus, of an improved transformer coil having a capacity wound primary.

Yet another object of the invention lies in the provision of an improved lead assembly for a spark discharge systern, such lead assembly including a novel transformer coil of the type above indicated.

Still another object of the invention lies in the provision of a transformer coil which is simpler, more economically made, and smaller than prior coils.

The above and further objects and novel features of the invention will more fully appear from the following description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only, and are not intended as a definition of the limits of the invention.

In drawings, wherein like reference characters refer to like parts throughout the several views,

FIG. 1 is a view in longitudinal axial section through a lead assembly employing a transformer coil made in accordance with the present invention as a part thereof, certain of the parts being shown in elevation;

FIG. 2 is a view in longitudinal axial section through a preliminarily formed portion of the transformer coil, such portion including a core form, a magnetic core therein, a wire wound secondary winding, and insulation on the secondary winding;

FIG. 3 is a somewhat schematic view in plan of the i transformer coil of FIG. 2, FIG. 3 showing the transformer coil during the assembly of the capacitively wound primary thereof;

FIG. 4 is a view in end elevation of the transformer coil during the assembling operation shown in FIG. 3;

FIG. 5 is a view in perspective of the assembled transformer coil of FIGS. 1 and 2, certain of the parts of the coil being shown broken away at one end thereof; and

FIG. 6 is a wiring diagram of an ignition circuit employing a lead assembly made in accordance with the invention.

Turning now to the drawings, a lead assembly, generally designated 10, is shown in FIG. 1. Such lead assembly may be employed, for example, in an ignition circuit for a jet engine. A typical ignition circuit in which the lead assembly 10 may be employed, shown in FIG. 6, will be described below.

In FIG. 1 there is shown a portion of a lead assembly designed for use between the main portion of the ignition circuit and an igniter plug of an engine. A contact pin 20 in a shell 12 at the left-hand end of the assembly is adapted to be received within a socket contact (not shown) connected to a lead wire (28' in FIG. 6) of the main portion of an ignition unit. An insulated cable 36, shown at the right in FIG. 1, extends to a suitable connector (not shown) by means of which the conductor is Patented June 2 2, 1965 attached to an igniter plug. A radio shielding metallic sheath 27, telescoped over cable 36, is secured as by welding a metal end piece 11. A tubular metallic shell 14, welded to the shell 12 of the connector part shown by an annular weld 17, and to an annular flange 16 on end piece 11 by an annular weld forms an enclosure constituting a part of the lead assembly and housing a voltage step-up transformer 31 made in accordance with the invention.

The contact pin 20 is centrally supported in an electrically insulating insert 19 which is retained in shell 12. Insert 19 has an axially inwardly extending annular portion which provides a seat 22 thereon for the reception of the end of an axially extending electrically insulating tube 21 which is positioned coaxially and radially inwardly of the sleeve 14. Such end of tube 21 abuts a shoulder 24 on insert 19, whereby the tube is positioned axially, as shown. The other end of tube 21 abuts the inner end face of flanged portion 25 of end piece 11 at an annular zone 26. The above-described enclosure protects and electrically insulates the transformer 31. As will appear hereinafter, after the assembly shown in FIG. 1 has been made, such enclosure, and also the space between sleeve 14 and tube 2.1, are preferably filled with a settable electrically insulating resin.

A lead wire 28 extends from the axially inner end of contact-20 to the input end of transformer 31. An output lead wire extends from coil 31 to the end of cable 36 which lies within the enclosure housing transformer 31, the lead wire and the conductor 39 of the cable being joined at 37. Preferably, cable 36 is knotted within the enclosure, as shown at 40, to relieve possible strain upon joint 37. j

The function of transformer 31 in an ignition system in accordance with the invention will be more readily apparent upon consideration of the wiring diagram of FIG. 6. Such system includes two input terminals 47 and 49, the first of which is adapted to be connected to the positive side of a direct current source, and the second of which, which is connected to ground, is adapted to be connected to the negative side of such source. Terminal 47 is connected through a conventional radio filter 50 to a vibrator 51 having contacts 52. The circuit includes a transformer 54, the circuit through the primary 55 of the transformer being periodically opened and closed by the vibrator contacts 52. The secondary 56 of transformer 54 is connected by a wire 59 to a rectifier 60 which, in turn, is connected by a wire 61 to a control gap 63. A resistor 68 is connected between ground and wire 28' in advance of the lead 10, as shown. A storage condenser 62 has one side thereof connected to ground by wire 64 and the other side connected to Wire 61, as shown. The condenser 62 is progressively charged by current pulses from transformer 54. After the charge on the condenser has reached a predetermined value, the condenser discharges through control gap 63 through the previously described lead wire assembly 11) and thence across the electrodes of an igniter gap 65. In the embodiment shown, the igniter gap is of the shunted type, wherein an electrically semi-conductive material bridges the electrodes of the gap. Such semi-conductive shunt is schematically indicated in FIG. 6 as a resistor 67. A first electrode of gap 65 is connected to the aforementioned conductor 39; the second electrode of the gap is connected to ground 66.

As shown in FIG. 1, the transformer 31 forms a part of the lead wire assembly disposed between Wire 28 and conductor 39. The transformer 31, as will more clearly appear hereinafter, has a capacitively wound primary 73 and a wire wound secondary 74. The wire wound secondary 74 is directly interposed between wires 28 and ,form, as shown.

3 39. A wire 82, connected to wire 28, is shown as extending to one terminal of the condenser-primary 73, the other terminal of the condenser being connected to ground by wire 34. The actual structure of transformer 31 employed in the illustrative embodiment is shown in FIGS. 2 and 5, such transformer being assembled in the manner schematically shown in FIGS. 3 and 4.

Transformer 31 has a core, generally designated 68, which is made up of a hollow electrically insulating coil form 69 within which is disposed a preformed magnetic core 70. V The magnetic core is retained within the core form by means of end closure discs cemented to the core In making the preliminary assembly shown in FIG. 2, lengths of insulating tape 71 are laid longitudinally upon the core form, and the secondary 74 of transformer 31 is then wound upon the core form. In an illustrative coil, the secondary is formed by a single layer of 45 turns of 22 gauge wire. After the secondary has been formed upon the core form, the ends of the insulating tape 71 are folded longitudinally inwardly over the secondary winding as indicated at 7 g in FIG. 2. The wire leads from the beginning and the end of the coil are designated 32 and 35, respectively.

The thus formed preliminary assembly 33 of FIG. 2 is now employed as a core for the winding of the capacitive primary thereon, as shown in FIGS. 3 and 4. Such primary winding, which also functions as a condenser, is made up of a plurality of layers of material which in combination are designated 73' in FIGS. 3 and 4. Layers 73' are made up of two outer longer layers 75 and '76 made of electrically insulating paper-like material such as mica paper, a shorter, intermediate foil 8% which may be, for example, aluminum foil, and two inner longer layers 77 and 79, made of material similar to that of layers '75 and 76. Two short layers of foil 81 and 84, disposed relatively to the other layers, as shown in FIGS. 3 and 4, complete the assembly 73. Layer 80 and short foil pieces 81 and 84 are generally of the same width and are somewhat narrower than layers 75, 76, 77, and 7%. Layer and foil pieces 81 and 84 are positioned in alignment, and with their side edges substantially equally spaced from the opposite side edges of the electrically insulating layers.

Layers 75, 76, 77, '79, and 80, assembled as shown in FIG. 4, are brought together at one end. Such preliminary assembly of layers is secured to 'the coil assembly 33 by short lengths of electrically insulating tape 83, as shown. Assembly 33 is now turned clockwise to wind the thus held layers of material upon it. After about one turn has been taken upon assembly 33, the short foil 31 is interposed between the layer 79 and the assembly 33 with the previously wound layers upon it. Foil 81 thus .overlaps the entering end of foil 81) but is separated therefrom by insulating layers 77 and 79. The Winding opera- .tion is then continued so that layer 81 becomes incorporated in the wound layers on the coil. At an ap-- propriate time in such further winding, the second short foil 84 is interposed between layers 79 and the previously wound layers on assembly 33. Foil 84 overlaps the trailing end of foil layer 80 as shown in FIG. 4. After the winding of the various layers upon the assembly 33 has been completed, the layers are held in tightly wound condition by the application of electrically insulating tapes 86 to the outside of the wound assembly.

In the final assembly, shown in FIG. 5, a lead strip 32, projecting laterally from foil layer 81, overlies and'is electrically connected to the lead wire 32 from the wound secondary coil. A similar lead strip 34, projecting laterally from foil layer 34, is connected to ground in the manner shown in FIG. 1. As there shown, lead strip 34 extends longitudinally within tube 21 and thence outwardly through a hole in such tube to be incorporated in the joint 15 between the end piece 11 and the outer metal tube 14 of unit 11?. The output lead 35 of the secondary coil projects from one end of transformer 31, as shown in FIGS. land 5.

After the assembly shown in FIG. 1 has been made, the housing of unit 19 is preferably filled and coated with an electrically insulating settable resin material. Thus the unit 1% may be filled with such material in liquid condition by causing it to how into the space within tube 21 through aligned holes 44 and 45 in tubes 14 and 21, respectively. Such resinous material will also flow into the space 42 between the tubes and completely fill it. Preferably, the resinous material also forms a coating over the outer surface of tube 14, the end surface of the radially outwardly projecting flange ortion of body 11, and the axially smaller diametered portion of such body, as indicated at 46 in phantom lines in FIG. 1. Such filling and coating operation may be carried out, for example, by positioning the assembly shown in FIG. 1 within a mold having a cavity of suitable shape and means to form a seal between such cavity between the larger diametered portion of shell 12, at one end of the cavity, and the smaller diametered portion of body 11 at the other end of the cavity. Such mold may be provided with appropriate means for introducing resinous material in liquid condition under pressure into the mold. The resinous material, introduced under pressure into the mold cavity, will flow along the exterior of tube 14 and through holes 44 and 45 in tubes 14' and 21, thus completely to fill the space within the housing of the assembly, as well as to provide a coating thereover. m

it will be seen that when the assembly 10 is employed in a circuit such as that shown in FIG. 6, the foil layer 81 taken with the other foil layers 84) and 84 function as a primary for the transformer 31. It will also be seen'that the foil layer 84, which is connected to the grounded housing of unit 1%, functions to ground the thus formed condenser in the manner indicated in FIG. 6. The layers 81, 8t and 84 thus function both as a wound primary of a voltage step-up transformer and as a condenser. The

resulting transformer 31 may be simply and economically made; because of its modest space requirements, such transformer may be includedas a part of an ignition lead assembly, without adding greatly to the weight and to the space required by such assembly.

Although only one embodiment of the invention has been illustrated in the accompanying drawings and described in the foregoing specification, it is to be especially understood that various changes, such as in the relative dimensions of the parts, materials used, and the like, as well as the suggested manner of use of the apparatus of the invention, may be made therein without departing from the spirit and scope of the invention as will now be apparent to those skilled in the art.

What is claimed is:

1. A radio-shielded electrical lead assembly comprising a metallic tube, a tubular end fitting telescoped with and secured to one end of said tube, a tubular insulator in said fitting, a connector contact supported in said insulator, an insulating tube having one end telescoped with the end of said insulator within said metallic tube, aprewound transformer having primary and secondary windings inserted into said insulating tube, means connecting one end of said primary winding and one end of said secondary winding to said contact, a second end fitting telescoped with and secured to the other end of said metallic tube in engagement with the other end of said insulating tube, a metallic conduit secured to said second fitting, an electrical conductor connected :to the other end of the secondary winding and extending through said second fitting and conduit, and means connecting the other end of said primary winding to said metallic tube.

2. An electrical lead assembly as defined in claim 1, wherein said pre-wound transformer comprises a metallic core, and wherein said secondary winding comprises a wire coil-wound on said core and said primary winding comprises at least two sheets of metallic foil separated by sheet insulation and wound around said secondary winding.

3. In a radio-shielded lead assembly, a metallic oasing comprising a metallic tube, first and second metallic end fittings at the ends of said tube and a metal conduit connected to said second end fitting, a tubular insulator in said first fitting, an insulating tube interposed between and positioned by said insulator and said second end fitting in said metallic tube, a pre-wound transformer inserted in said insulating tube, a connector contact supported in said insulator, means connecting said contact to the primary and secondary windings of the transformer, an electrical conductor extending through said conduit and connected to said secondary winding, and means connecting the primary winding to said casing.

4. A lead assembly as defined in claim 3 comprising a solid insulating material substantially filling the remaining space in said metallic tube.

5. A lead assembly as defined in claim 3, wherein the primary winding of said transformer consists essentially of at least two spirally wound metallic sheets separated by insulating sheets, whereby said primary Winding functions also as a capacitor.

6. A combination transformer-condenser comprising an insulated metallic core, a wire coil-wound around said core .and constituting the secondary winding of a transformer, and at least two layers of sheet metal separated by sheet insulation spirally wound around said core to function as an electrical condenser and in inductive coupling relation with said secondary winding to constitute the primary winding of the transformer.

7. In an electrical device, a core comprising magnetic metal, a wire coil wound around said core and constituting the secondary winding of a transformer, and a combined condenser-primary winding comprising a first sheet of metal, second and third sheets of metal disposed in overlapping relation with opposite end portions of said first sheet, and sheet insulation separating said first sheet from said second and third sheets, said metallic sheets and sheet insulation being spirally wound around the .said core with said metallic sheets in inductive coupling relation with said secondary Winding, and terminal means connected to said second and third metallic sheets.

References Cited by the Examiner UNITED STATES PATENTS 2,378,893 6/45 Berkey et al.

2,414,692 1/47 Harkness et al.

2,533,716 12/50 Coursey 317260 FOREIGN PATENTS 841,434 7/60 Great Britain.

SAMUEL BERNSTEIN, Primary Examiner.

JAMES D. KALLAM, Examiner. 

1. A RADIO-SHIELDED ELECTRICAL LEAD ASSEMBLY COMPRISING A METALLIC TUBE, A TUBULAR END FITTING TELESCOPED WITH AND SECURED TO ONE END OF SAID TUBE, A TUBULAR INSULATOR IN SAID FITTING, A CONNECTOR CONTACT SUPPORTED IN SAID INSULATOR, AN INSULATING TUBE HAVING ONE END TELESCOPED WITH THE END OF SAID INSULATOR WITHIN SAID METALLIC TUBE, A PREWOUND TRANSFORMER HAVING PRIMARY AND SECONDARY WINDINGS INSERTED INTO SAID INSULATING TUBE, MEANS CONNECTING ONE END OF SAID PRIMARY WINDING AND ONE END OF SAID SECONDARY WINDING TO SAID CONTACT, A SECOND END FITTING TELESCOPED WITH AND SECURED TO THE OTHER END OF SAID METALLIC TUBE IN ENGAGEMENT WITH THE OTHER END OF SAID INSULATING TUBE, A METALLIC CONDUIT SECURED TO SAID SECOND FITTING, AN ELECTRICAL CONDUCTOR CONNECTED TO THE OTHER END OF THE SECONDARY WINDING AND EXTENDING THROUGH SAID SECOND FITTING AND CONDUIT, AND MEANS CONNECTING THE OTHER END OF SAID PRIMARY WINDING TO SAID METALLIC TUBE. 